2.5 is not going to hurt you at your current power levels. IIRC Andy competed in the first TOTB with a 2.5 system.
However, as they are the same price I opted for a 3 inch system when I was buying mine. You'll barely notice any differnce in the spoll and will give you more headroom if you want more power later on. Makes it a bit louder too but I don't know if you'd consider that a pro or a con.
P.s. how the family Cal, you got the hang of your new life yet?